Re: [PATCH v2 1/2] KVM: VMX: Cleanup VMX basic information defines and usages

[Huang, Kai]

>  
> +/* VMX_BASIC bits and bitmasks */
> +#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY		BIT_ULL(48)
> +#define VMX_BASIC_MEM_TYPE_WB			6LLU

Strictly speaking, VMX_BASIC_MEM_TYPE_MB isn't any bit definition or bitmasks of
VMX_BASIC MSR.  So perhaps better to put it somewhere under separately.
 
> +#define VMX_BASIC_INOUT				BIT_ULL(54)
> +
> +/* VMX_MISC bits and bitmasks */

Your next patch is to "Cleanup VMX misc information defines and usages", so I
guess it's better to move any VMX_MISC related change to that patch.

>  #define VMX_MISC_PREEMPTION_TIMER_RATE_MASK	0x0000001f
>  #define VMX_MISC_SAVE_EFER_LMA			0x00000020
>  #define VMX_MISC_ACTIVITY_HLT			0x00000040
> @@ -143,6 +149,16 @@ static inline u32 vmx_basic_vmcs_size(u64 vmx_basic)
>  	return (vmx_basic & GENMASK_ULL(44, 32)) >> 32;
>  }
>  
> +static inline u32 vmx_basic_vmcs_basic_cap(u64 vmx_basic)
> +{
> +	return (vmx_basic & GENMASK_ULL(63, 45)) >> 32;
> +}
> +
> +static inline u32 vmx_basic_vmcs_mem_type(u64 vmx_basic)
> +{
> +	return (vmx_basic & GENMASK_ULL(53, 50)) >> 50;
> +}
> +
>  static inline int vmx_misc_preemption_timer_rate(u64 vmx_misc)
>  {
>  	return vmx_misc & VMX_MISC_PREEMPTION_TIMER_RATE_MASK;
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 4ba46e1b29d2..274d480d9071 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -1201,23 +1201,34 @@ static bool is_bitwise_subset(u64 superset, u64 subset, u64 mask)
>  	return (superset | subset) == superset;
>  }
>  
> +#define VMX_BASIC_VMCS_SIZE_SHIFT		32
> +#define VMX_BASIC_DUAL_MONITOR_TREATMENT	BIT_ULL(49)
> +#define VMX_BASIC_MEM_TYPE_SHIFT		50
> +#define VMX_BASIC_TRUE_CTLS			BIT_ULL(55)

If I am reading correctly, the two "*_SHIFT" above are not used?  The above
vmx_basic_vmcs_mem_type() and vmx_basic_vmcs_basic_cap() use hard-coded values
directly.

And How about moving all these bit/mask definitions to <asm/vmx.h> above?

It's better they stay together for better readability.

> +
> +#define VMX_BASIC_FEATURES_MASK			\
> +	(VMX_BASIC_DUAL_MONITOR_TREATMENT |	\
> +	 VMX_BASIC_INOUT |			\
> +	 VMX_BASIC_TRUE_CTLS)
> +
> +#define VMX_BASIC_RESERVED_BITS			\
> +	(GENMASK_ULL(63, 56) | GENMASK_ULL(47, 45) | BIT_ULL(31))
> +

Also move these to <asm/vmx.h>?

>  static int vmx_restore_vmx_basic(struct vcpu_vmx *vmx, u64 data)
>  {
> -	const u64 feature_and_reserved =
> -		/* feature (except bit 48; see below) */
> -		BIT_ULL(49) | BIT_ULL(54) | BIT_ULL(55) |
> -		/* reserved */
> -		BIT_ULL(31) | GENMASK_ULL(47, 45) | GENMASK_ULL(63, 56);
>  	u64 vmx_basic = vmcs_config.nested.basic;
>  
> -	if (!is_bitwise_subset(vmx_basic, data, feature_and_reserved))
> +	static_assert(!(VMX_BASIC_FEATURES_MASK & VMX_BASIC_RESERVED_BITS));
> +
> +	if (!is_bitwise_subset(vmx_basic, data,
> +			       VMX_BASIC_FEATURES_MASK | VMX_BASIC_RESERVED_BITS))
>  		return -EINVAL;
>  
>  	/*
>  	 * KVM does not emulate a version of VMX that constrains physical
>  	 * addresses of VMX structures (e.g. VMCS) to 32-bits.
>  	 */
> -	if (data & BIT_ULL(48))
> +	if (data & VMX_BASIC_32BIT_PHYS_ADDR_ONLY)
>  		return -EINVAL;
>  
>  	if (vmx_basic_vmcs_revision_id(vmx_basic) !=
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 4c3a70f26b42..b68d54f6e9f8 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2568,14 +2568,13 @@ static u64 adjust_vmx_controls64(u64 ctl_opt, u32 msr)
>  static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
>  			     struct vmx_capability *vmx_cap)
>  {
> -	u32 vmx_msr_low, vmx_msr_high;
>  	u32 _pin_based_exec_control = 0;
>  	u32 _cpu_based_exec_control = 0;
>  	u32 _cpu_based_2nd_exec_control = 0;
>  	u64 _cpu_based_3rd_exec_control = 0;
>  	u32 _vmexit_control = 0;
>  	u32 _vmentry_control = 0;
> -	u64 misc_msr;
> +	u64 vmx_basic;
>  	int i;
>  
>  	/*
> @@ -2693,28 +2692,26 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
>  		_vmexit_control &= ~x_ctrl;
>  	}
>  
> -	rdmsr(MSR_IA32_VMX_BASIC, vmx_msr_low, vmx_msr_high);
> +	rdmsrl(MSR_IA32_VMX_BASIC, vmx_basic);
>  
>  	/* IA-32 SDM Vol 3B: VMCS size is never greater than 4kB. */
> -	if ((vmx_msr_high & 0x1fff) > PAGE_SIZE)
> +	if ((vmx_basic_vmcs_size(vmx_basic) > PAGE_SIZE))
>  		return -EIO;
>  
>  #ifdef CONFIG_X86_64
>  	/* IA-32 SDM Vol 3B: 64-bit CPUs always have VMX_BASIC_MSR[48]==0. */
> -	if (vmx_msr_high & (1u<<16))
> +	if (vmx_basic & VMX_BASIC_32BIT_PHYS_ADDR_ONLY)
>  		return -EIO;
>  #endif
>  
>  	/* Require Write-Back (WB) memory type for VMCS accesses. */
> -	if (((vmx_msr_high >> 18) & 15) != 6)
> +	if (vmx_basic_vmcs_mem_type(vmx_basic) != VMX_BASIC_MEM_TYPE_WB)
>  		return -EIO;
>  
> -	rdmsrl(MSR_IA32_VMX_MISC, misc_msr);
> -
> -	vmcs_conf->size = vmx_msr_high & 0x1fff;
> -	vmcs_conf->basic_cap = vmx_msr_high & ~0x1fff;
> +	vmcs_conf->size = vmx_basic_vmcs_size(vmx_basic);
> +	vmcs_conf->basic_cap = vmx_basic_vmcs_basic_cap(vmx_basic);
>  
> -	vmcs_conf->revision_id = vmx_msr_low;
> +	vmcs_conf->revision_id = vmx_basic_vmcs_revision_id(vmx_basic);

I actually tried to do similar thing before, and Sean gave me below advice:

	Rather than do all of these weird dances, what about saving the
full/raw
	MSR in the config, and then using the helpers to extract info as
needed? 

https://lkml.kernel.org/kvm/20230330092149.101047-1-kai.huang@xxxxxxxxx/T/#m4879a3c7e66ede7bfa568a25aea4f6e3778e6e34

I agreed, but I has been too lazy to do this, sorry :-)

So maybe we should still go with this approach?

>  
>  	vmcs_conf->pin_based_exec_ctrl = _pin_based_exec_control;
>  	vmcs_conf->cpu_based_exec_ctrl = _cpu_based_exec_control;
> @@ -2722,7 +2719,8 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
>  	vmcs_conf->cpu_based_3rd_exec_ctrl = _cpu_based_3rd_exec_control;
>  	vmcs_conf->vmexit_ctrl         = _vmexit_control;
>  	vmcs_conf->vmentry_ctrl        = _vmentry_control;
> -	vmcs_conf->misc	= misc_msr;
> +
> +	rdmsrl(MSR_IA32_VMX_MISC, vmcs_conf->misc);

Better to move VMX_MISC code to next patch I suppose.